Safety improvements for airport runways and taxiways

ABSTRACT

An airstrip shoulder-bordering surface arrangement for extending the width of existing runway and taxiway shoulders comprising a flexible water-impermeable surfacing material extending laterally of a side edge of an airstrip shoulder, an artificial grass surface adjacent the water-impermeable surfacing material, and an edge-fastening system for securing the surfacing material in position relative to the airstrip shoulder and prevent water migration therebetween, the surfacing material having a relatively smooth top surface.

This application claims the benefit of Provisional U.S. Appl. No.60/369,334, filed Apr. 3, 2002.

FIELD OF THE INVENTION

The present invention relates to safety improvements for airporttaxiways and runways and particularly to the need to increase the widthof taxiways and runways at airports in order to minimize the risk offoreign object damage to aircraft engines, as well as the safety issuesregarding the deterioration of the existing natural grass surfacesbounding taxiways and runways.

BACKGROUND OF THE INVENTION

With the advent of larger and more powerful planes circulating onairport runways and taxiways that were constructed many years ago, thereis a serious safety concern regarding overhanging engines which nowfrequently extend well beyond the existing runway and taxiway shoulders.The new generation of aircraft presently being manufactured have verylarge wing spans resulting in the jet engines overlapping the existingrunway and taxiway shoulders, and in many cases actually hanging overthe natural grass areas bounding the runway or taxiway, thus greatlyincreasing the risk of damage to aircraft engines by the presence offoreign objects.

The majority of airport runway and taxiway shoulders are constructed ofasphalt which may have deteriorated surfaces and edges, such as crackingand spalling. This creates a serious risk of damage to aircraft andparticularly aircraft engines overhanging the airstrip shoulders causedby foreign objects such as loose pieces of asphalt and debris that couldbe ingested by the aircraft engines. Foreign object damage is a primarysafety concern for both airport operators and aircraft manufacturerssince it could have catastrophic results. In addition to foreign objectdamage potential, asphalt pavements require periodic maintenance and/orcomplete replacement which adds to the overall airport operation costs.

In order to minimize the risk of foreign object damage to aircraftengines and in order to comply with regulatory safety issues, onesolution is to increase the width of existing runways and taxiways usingconcrete or asphalt placed over deep bases in traditional constructionmethods. However, the costs related to traditional construction methodsand to airport operation down-time resulting from the traditionalconstruction are very significant and in some cases not feasible.

Air fields are generally constructed in large open areas and so inaddition to jet blasts and vortex shedding, they are exposed to windstorms, ice and snow storms as well as sand storms, which requiresexpensive maintenance of existing topsoil bounding the runways andtaxiways, such as cutting, grooming, cleaning, etc., in order to ensureefficient surface drainage of water, and to avoid water ponding andpossibly freezing of the surface water on the runway.

Therefore, there is a need for improvement of airport runways andtaxiways, particularly the need for improvements of the extension ofexisting runway and taxiway shoulders.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method for improvingsafety of airport runways and taxiways.

Another object of the present invention is to provide a cost-effectivesolution for the extension of existing runway and taxiway shoulders atairports in order to minimize the risk of foreign object damage toaircraft engines.

A further object of the present invention is to provide an airportrunway and taxiway shoulder-bordering surface arrangement to extend thewidth of existing runway and taxiway shoulders, thereby reducing thepotential for damage to aircraft engines by foreign objects.

In accordance with a general aspect of the present invention, there isprovided a method for improving safety of airport airstrips comprisingsteps of:

-   a) providing a flexible surfacing material; and-   b) extending the width of an existing shoulder of the airstrip by    installing said flexible surfacing material along a side of said    airstrip.

In accordance with a more specific aspect of the present invention, themethod comprises the steps of: providing a compacted soil base boundinga shoulder of an airstrip; placing a flexible, water-impermeablesurfacing material on the compacted soil base; and anchoring thesurfacing material to the airstrip in a water-tight manner so that thesurfacing material will assure efficient surface drainage of water andallow for unobstructed run-off of loose particles.

It is preferable to further lay a synthetic grass surface on an areabeyond the surfacing material so that loose particles can be trappedthereby when being driven by jet blasts from the airstrip and runningoff the surfacing material.

In accordance with another aspect of the present invention, an airportrunway and taxiway shoulder-bordering surface arrangement is provided toextend the width of existing runway and taxiway shoulders, therebyeliminating the potential for damage to aircraft engines by looseparticles. The arrangement comprises a compacted soil base bounding anairstrip and a flexible water-impermeable surfacing material placed onthe compacted soil base and directly adjacent to a side edge of theairstrip. Means are provided for anchoring the surfacing material to theedge of the airstrip in a water-tight manner so that the surfacingmaterial will assure efficient surface drainage of water and allow forunobstructed run-off of loose particles. It is noted that the flexiblewater-proof surfacing material can be installed directly on the existingpaved airstrip shoulder area in order to reduce the cost of excavatingthe existing asphalt and to keep the existing shoulder in place.

In accordance with a further general aspect of the present invention,there is provided an airfield safety arrangement for reducing the riskthat an aircraft engine be damaged as a result of the ingestion offoreign objects from an area adjacent an airstrip, the safetyarrangement comprising a ground surfacing material adapted to be laiddown on the ground so as to extend laterally outwardly from an airstrip,the ground surfacing material having a relatively smooth sheddingsurface sloping downwardly from the airstrip to provide for surfacewater drainage and run-off of loose particles to a location wherein theparticles are not subject of being ingested by the engines of theaircrafts on the airstrip, and an edge anchoring system for bonding theground surfacing material in a water-tight manner to the airstrip. Thesurfacing material may be provided with a textured pattern as long as itdoes not impede run-off of loose particles.

Still in accordance with the present invention, there is provided anairstrip shoulder-bordering surface arrangement for extending the widthof existing runway and taxiway shoulders in order to reduce thepotential for damage to aircraft engines by foreign objects (FOD), thearrangement comprising a flexible water-impermeable surfacing materialadapted to extend laterally of a side edge of an airstrip shoulder; andan edge-fastening system for securing the surfacing material in positionrelative to the airstrip shoulder and prevent water migrationtherebetween, the surfacing material having a relatively smooth topsurface to provide for water surface drainage and unobstructed run-offof loose particles.

The surfacing material preferably further includes reflective andluminescent materials (for instance phosphorescent materials) to provideperimeter lines and runway identification markings so that in situationswhere the luminescent effect of the reflective materials has faded theaircraft lights would be reflected. The reflective or luminescentmaterials can be provided as an integral part of the surfacing materialor can be applied thereon such as by bonding, painting or other by usingany other appropriate techniques. The surfacing material is preferablyin a green colour, or could be other colours if required to make astrong visual contrast between the runway and taxiway edges and the edgeof the natural field.

In another embodiment of the present invention, the arrangement furtherincludes a synthetic grass surface covering an area beyond the surfacingmaterial which is permanently bonded to the surfacing material. Thus,the relatively smooth texture of the surfacing material will allow forunobstructed run-off of any loose particles that might be present on therunway and taxiway shoulders and could present a potential for foreignobject damage to aircraft engines. As an added value, the replacement ofnatural grass surfaces with the surfacing material in combination withthe synthetic grass surface can provide considerable cost benefits withregards to airport maintenance budgets. This artificial grass can beeither permeable or impermeable depending on the specifications for thespecific application.

Substantial savings in airport maintenance budgets can be achieved withthe installation of the surfacing material which is virtuallymaintenance free. In addition, the installation of the synthetic grasssurface would eliminate the need for the trimming and cutting of naturalgrasses. The artificial grass would retain its permanent green colourand texture throughout the year, thus eliminating the need to re-sod oldand dead natural grass. In hot and arid climates, for example, in theMiddle East, the relatively smooth shedding surface of the surfacingmaterial would allow the removal of sand and other loose foreign objectsquickly and efficiently from the shoulders simply as a result of thewind or air turbulence created by aircrafts or other mechanical means.Regular maintenance to keep the extended shoulders free of hazardousdebris can be conducted easily, quickly and economically. The debris isdisplaced into the adjacent synthetic grass turf where the debris willbe trapped. If necessary the accumulated debris can be vacuumed outperiodically.

In cold climates accumulated snow can be easily and quickly removed fromthe surfacing material either by large blowers or sweepers, to adistance beyond the overhang of aircraft engines.

Since the surfacing material is completely water-tight, the risk ofsettlement and deterioration of the supporting base would be eliminated,thus providing a stable base for maintenance vehicle circulationyear-round.

The pattern of installation of the surfacing material with the seamsrunning parallel to the existing shoulder edges would not interfere withmaintenance operations.

Other advantages and features of the present invention will be betterunderstood with reference to preferred embodiments thereof describedhereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus generally described the nature of the invention, referencewill now be made to the accompanying drawings, showing by way ofillustration a preferred embodiment thereof, and in which:

FIG. 1 is a perspective view of an airport runway having shoulderextensions in accordance with a preferred embodiment of the presentinvention;

FIG. 2 is a cross-sectional view of an airstrip shoulder-borderingarrangement in accordance with a first embodiment of the presentinvention; and

FIG. 3 is a cross-sectional view of an airstrip shoulder-borderingarrangement in accordance with a second embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates an airport runway 10 comprising a centraltake-off/landing strip 11 and a pair of runway shoulders 12. Eachshoulder 12 is extended laterally outwardly by means of ashoulder-bordering arrangement comprising a soft ground cover orflexible water-proof surfacing material 14.

As shown in FIG. 2, the installation of the surfacing material 14normally begins with a first step of removing the existing organicmaterial contained in the uppermost stratum of the ground G bounding theshoulders 12 of the runway or taxiway which is generally referred to asan airstrip throughout this application, to a depth dictated by the soilreport. The ground G is excavated down to a compactable earth surface.At that point, the soil is graded and compacted by being rolled andshaped to meet the required slopes such that the flow of surface waterwill be controlled to drain to specific locations. The rocks are removedfrom the compacted soil base and if required, a layer of engineeredbackfill will be installed and compacted prior to installing thesurfacing material 14 directly on the compacted backfill if specified todo so. It is noted that in some applications, the surfacing material 14may be laid down directly on the ground without the need for excavating.

The flexible surfacing material 14, which is a plastic composite, forexample polypropylene, urethane, vinyl or polyethylene, is laid directlyon the compacted soil base adjacent to the edge of the existing airstripshoulder 12. As shown in FIG. 3, the surfacing material 14 may also beinstalled so as to at least partly cover or overlap the shoulder 12 ofthe airstrip (i.e. the runway or the taxiway). This is particularlyapplicable in the case where the existing shoulder would have to berepaired or re-paved. The surfacing material 14 has a relatively smoothtexture having a thickness of between 50 mm and 400 mm. The surfacingmaterial 14 can be provided in the form of a polyethylene, polypropyleneor any other type of plastic or composite material that can be sprayedor laminated upon a mesh substrate. The polyethylene or any equivalentthereof could be sprayed or applied by various methods on site or at themanufacturing plant. The surfacing material 14 is completelywater-impermeable and is preferably permanently bonded to anedge-fastening system or anchoring system 16 placed next to the existingairstrip shoulder edges or to the shoulder 12 directly since allinstallations are different.

The installation of the surfacing material 14 is completed byoverlapping rolls of the surfacing material and applying a heattreatment, such as thermal welding, or by applying adhesives to theoverlapping surfacing materials, thus fusing the two materials togetherto obtain a permanent, water-tight and strong bonding of the seams.

In the illustrated embodiment, the surfacing material 14 is bonded in awater-tight manner to the airstrip shoulder 12. More particularly, theinterface between the edge of the existing airstrip shoulders and thefirst roll of the surfacing material can be made water-tight byinstalling impermeable elastomeric sealers in order to assure acontinuous and uninterrupted surface drainage of the impermeablesurface. The impermeable elastomeric sealer is incorporated with thespecially designed anchoring system 16 which assures the safe, permanentand economical anchoring of the edges of the surfacing material 14 tothe immediately adjacent existing airstrip shoulders 12.

The anchoring system 16 preferably includes a prefabricated, extrudedplastic member 18, for example polypropylene or other plastic that canbe thermally bonded to the flexible surfacing material 14. The extrudedplastic member 18 is partially embedded in specially formulatedexpanding foam 20 which is injected into a narrow excavated trench alongthe edge of the airstrip shoulder 12. The excavation, injection of foam,and bonding of the plastic member 18 are completed simultaneously in oneoperation. The plastic member 18 has an anchoring portion 24 from whichextends a leg 26 supporting an above-ground section or head 22 to whichthe first row of surfacing material 14 is thermally or mechanicallybonded. For instance, bonding of the surfacing material 14 can be doneby applying a heat activated treatment or by applying adhesives to theoverlapping of the surfacing material 14 and the extruded plastic member18, thus permanently fusing the two materials together. This anchoringsystem 16 provides a water-tight seal between the airstrip shoulder edgeand the surfacing material 14. A sealer 27 is preferably provided alongthe vertical interface between the shoulder 12 and the ground surfacingarrangement, as shown in FIG. 2.

When the entire surfacing material 14 is in place, the surfacingmaterial 14 will take the shape and the slope of the underlyingcompacted soil base and will stay flat to provide the relatively smoothshedding surface to provide for water drainage and run off of looseparticles. The extent in width and length to which the surfacingmaterial 14 is installed will depend on the performance and designcriteria of the specific sites. The areas beyond the surfacing material14 could be covered with artificial grass 30 which would trap any bornparticles, such as sand displace by aircraft. The synthetic grasssurface is permanently bonded to the surfacing material 14 such as byapplying the thermal welding technique or by applying adhesives toassure a permanent water-tight seam between the surfacing material 14and the synthetic grass surface 30.

The synthetic grass surface 30 generally includes a pile fabric 32 whichis preferably placed over a compacted soil base substantially free oforganic matter. The pile fabric 32 includes a plurality of pile elements34 resembling blades of grass and extending from a relatively thin andflexible backing mat 36 to a predetermined height thereabove. Anon-water retaining ballast material 38 for stabilizing the pile fabric32 in place is provided on the backing mat 36 and has a thickness lessthan the predetermined height of the pile elements 34. The ballastmaterial 38 is provided in the form of a relatively thick layer ofparticulate material dispersed among the pile elements 34 on the backingmat 36. The synthetic grass is typically installed on a sloped base fordirecting water from the pile fabric 32 to the designed storm watermanagement system. Surface drainage is important since it is easier toprepare and can work at lower cost.

The rows of pile elements 34 can be similar to that described inApplicant's co-pending Canadian Patent 2,218,314 filed on Oct. 16, 1997,and laid open on Sep. 10, 1998, the contents of which are incorporatedherein by reference.

A thin impermeable membrane 40 is laid on the compacted soil base toprevent water from percolating down thereto. A drainage enabling layer42 which comprises a thick layer of aggregate, such as rockparticulates, is provided on the impermeable membrane 40. The flexiblebaking mat 36 is placed on the drainage enabling layer 42 so that thewater can readily flow from the backing mat 36 through the drainageenabling layer 42 onto the impermeable membrane 40 and into storm sewersplaced at strategic locations. This embodiment is described with moredetails in Applicant's PCT application PCT/CA01/01275, entitledARTIFICIAL GRASS FOR LANDSCAPING, filed Sep. 5, 2001, the specificationsof which is incorporated herein by reference. It is noted that the waterbarrier could be integrated to the backing mat 36 in which case theinfill layer 38 would act as the drainage enabling layer.

As shown in FIG. 2, the surfacing material 14 can be bonded to the edgeof the impermeable membrane 40 to provide a water-tight seal between thesynthetic grass surface 30 and the surfacing material 14. Alternatively,the surfacing material could be placed underneath the backing mat 36 andbe thermally or adhesively bonded thereto.

As an added safety feature, the surfacing material 14 can be fabricatedwith a permanent colour such as green, or with other colours if requiredto enhance visual contrast between the central landing zone of theairstrip 10 and the shoulders 12 thereof. The surfacing material 14 canalso be designed to accept solar energy absorbing fabrics which willdissipate a luminescent glow during the night without the need ofoutside power sources. The luminescent reflective glow would last up to10–12 hours to cover the dusk to dawn period. The solar absorbing fabriccan be coated directly onto the installed surfacing material 14 or canbe installed during fabrication. Patterns spacing and shape factors canbe custom fabricated to meet specific airport operation specifications.The solar absorbing fabric can advantageously replace conventionallighting systems for small airports.

The surfacing material 14 can further include special reflective fabricsinstalled thereon to enhance the visibility of the runway path foraircraft landing during the night. Thus in situations where theluminescent effect of the solar absorbing fabric fades, the aircraftlights will be reflected by the one-way reflective fabrics to facilitatesafe landing.

As shown in FIG. 3, the surfacing material 14 can be installed directlyon an existing shoulder 12 and anchored thereto by means of an anchormember 18′ provided in the form of a plastic extrusion placed in atrench formed in the shoulder 12 and fixed in position therein by meansof a plurality of anchoring bars. The surfacing material 14 can bethermally or adhesively bonded to the anchor member 18′ or evenmechanically attached thereto, as described hereinbefore with respect toFIG. 2. Alternatively, the surfacing material 14 could be adhesivelybonded directly to the shoulder 12. A given thickness of material isremoved from the shoulders 12 so that the surfacing material 14 issubstantially flush with the take-off/landing strip 11.

Protection against foreign object damage (FOD) can be further enhancedby incorporating a guidance system into the surfacing material forguiding a robot 48 parallel the runway 10 in order to locate and detectFOD materials that could be ingested by the aircraft engines. Theguidance system could include a magnetic guidance wire 46 embedded inthe surfacing material 14 or any other type of guidance technology.

By having guidance wires embedded into the flexible surfacing material14, drainage of the runway would not be impeded by channels orprotruding edges to guide the robots 48. The robots 48 could also bedesigned to clear the flexible fabric of sand and FOD by means of havinga larger robot made with the necessary blowers to do so. The FODdetecting robot would need to be heavy and stable enough to not bedisplaced from the wind and or jet wash. A cable system could also beused to guide the robot along and keep the robot tethered.

Modifications and improvements to the above-described embodiment of thepresent invention may become apparent to those skilled in the art. Theforegoing description is intended to be exemplary rather than limiting.The scope of the invention is therefore intended to be limited solely bythe scope of the appended claims.

1. An airstrip shoulder-bordering surface arrangement for extending the width of existing runway and taxiway shoulders in order to reduce the potential for damage to aircraft engines by foreign objects (FOD), the arrangement comprising: an exposed flexible water-impermeable surfacing material extending laterally of a side edge of an airstrip shoulder; an artificial grass surface adjacent the water-impermeable surfacing material; and an edge-fastening system for securing the surfacing material in position relative to the airstrip shoulder and prevent water migration therebetween, the surfacing material having a relatively smooth top surface to provide for water surface drainage and unobstructed run-off of loose particles.
 2. An airstrip shoulder-bordering surface arrangement as defined in claim 1, wherein said flexible water-impermeable surfacing material slopes from the edge of the airstrip shoulder to the artificial grass adapted to trap the loose particles running-off the surfacing material.
 3. An airstrip shoulder-bordering surface arrangement as defined in claim 2, wherein a water-tight joint is provided between the artificial grass and the surfacing material.
 4. An airstrip shoulder-bordering surface arrangement as defined in claim 2, wherein said artificial grass is heat bonded to said surfacing material.
 5. An airstrip shoulder-bordering surface arrangement as defined in claim 1, wherein said surfacing material is made of a plastic composite material.
 6. An airstrip shoulder-bordering surface arrangement as defined in claim 5, wherein said plastic composite material is selected from a group consisting of: polypropylene, urethane, vinyl and polyethylene.
 7. An airstrip shoulder-bordering surface arrangement as defined in claim 1, wherein said surfacing material is laid on a layer of compacted engineered base material.
 8. An airstrip shoulder-bordering surface arrangement as defined in claim 1, wherein said edge-fastening system includes an anchor partly buried in the soil along the side edge of the airstrip shoulder, said anchor having a head bonded to a longitudinal side edge of said surfacing material.
 9. An airstrip shoulder-bordering surface arrangement as defined in claim 8, wherein said anchor is provided in the form of an extrusion having a bottom anchoring portion connected to said head via an upstanding leg portion.
 10. An airstrip shoulder-bordering surface arrangement as defined in claim 9, wherein said above-ground portion is thermally fused to said longitudinal side edge of said surfacing material.
 11. An airstrip shoulder-bordering surface arrangement as defined in claim 8, wherein said anchor is partly embedded in expansion foam.
 12. An airstrip shoulder-bordering surface arrangement as defined in claim 1, wherein airstrip markings are provided on said surfacing material, said airstrip markings being made of at least one of a reflective material and a luminescent material.
 13. An airstrip shoulder-bordering surface arrangement as defined in claim 12, wherein said surfacing material is of a different color than the airstrip in order to enhance visual contrast between the airstrip and the shoulders thereof.
 14. An airstrip shoulder-bordering surface arrangement as defined in claim 1, wherein a guidance system is incorporated to said surfacing material to guide a robot along the airstrip in order to locate and detect FOD materials susceptible of being ingested by an aircraft engine.
 15. An airstrip shoulder-bordering surface arrangement for extending the width of existing runway and taxiway shoulders in order to reduce the potential for damage to aircraft engines by foreign objects (FOD), the arrangement comprising: a flexible water-impermeable surfacing material extending laterally of a side edge of an airstrip shoulder, the surfacing material having a relatively smooth top surface to provide for water surface drainage and unobstructed run-off of loose particles; an artificial grass surface adjacent the water-impermeable surfacing material; and an edge-fastening system for securing the surfacing material in position relative to an airstrip shoulder and prevent water migration therebetween, the edge fastening system comprising: an anchor adjacent the side edge of the airstrip shoulder, said anchor having a head bonded to a longitudinal side edge of said surfacing material and wherein said anchor and said shoulder form a fluid-tight seal.
 16. An airstrip shoulder-bordering surface arrangement according to claim 15, wherein the anchor is at least partially embedded in expansion foam.
 17. An airstrip shoulder-bordering surface arrangement according to claim 15, further comprising a sealer between the anchor and the airstrip shoulder.
 18. An airstrip shoulder-bordering surface arrangement according to claim 15, wherein said anchor is provided in the form of an extrusion having a bottom anchoring portion connected to said head via an upstanding leg portion.
 19. An airstrip shoulder-bordering surface arrangement as defined in claim 15, wherein said above-ground portion is thermally fused to said longitudinal side edge of said surfacing material. 